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An Agro-Climatological
Characterization of Bread Wheat
Production Areas in Ethiopia
Jeffrey W. White,1 Douglas G. Tanner,2 and John D. Corbett3
Published jointly by theWheat Program
and the
Natural Resources Group
Geographic Information SystemsSeries 01-01
1 GIS and Modeling Lab, Natural Resources Group, CIMMYT 2 Agronomist, CIMMYT Wheat Program, Addis Ababa, Ethiopia3 Blackland Research and Extension Center, the Texas A&M University Research System
INTERNATIONAL MAIZE AND WHEAT
IMPROVEMENT CENTER
CIMMYT® (www.cimmyt.org) is an internationally funded, nonprofit, scientific research and training organization. Headquartered in Mexico, CIMMYT works with agricultural research institutions worldwide to improve the productivity, profitability, and sustainability of maize and wheat systems for poor farmers in developing countries. It is one of 16 food and environmental organizations known as the Future Harvest Centers. Located around the world, the Future Harvest Centers conduct research in partnership with farmers, scientists, and policymakers to help alleviate poverty and increase food security while protecting natural resources. The centers are supported by the Consultative Group on International Agricultural Research (CGIAR) (www.cgiar.org), whose members include nearly 60 countries, private foundations, and regional and international organizations. Financial support for CIMMYT’s research agenda also comes from many other sources, including foundations, development banks, and public and private agencies.
Future Harvest® builds awareness and support for food and environmental research for a world with less poverty, a healthier human family, well-nourished children, and a better environment. It supports research, promotes partnerships, and sponsors projects that bring the results of research to rural communities, farmers, and families in Africa, Asia, and Latin America (www.futureharvest.org).
© International Maize and Wheat Improvement Center (CIMMYT) 2001. All rights reserved. The opinions expressed in this publication are the sole responsibility of the authors. The designations employed in the presentation of materials in this publication do not imply the expression of any opinion whatsoever on the part of CIMMYT or its contributory organizations concerning the legal status of any country, territory, city, or area, or of its authorities, or concerning the delimitation of its frontiers or boundaries. CIMMYT encourages fair use of this material. Proper citation is requested.
Correct citation: White, J.W., D.G. Tanner, and J.D. Corbett. 2001. An Agro-Climatological Characterization of Bread Wheat Production Areas in Ethiopia. NRG-GIS Series 01-01. Mexico, D.F.: CIMMYT.
Abstract: This report describes a GIS-based assessment of the distribution of wheat production in Ethiopia, with emphasis on climate factors limiting the potential wheat area and using mainly agro-climatological characteristics obtained from interpolated climate data contained in the Ethiopian Country Almanac. Results suggest that the greatest opportunity for expanding wheat production in Ethiopia would involve increasing the tolerance of wheat to warmer growing conditions but that other factors, including the adaptation of current and/or alternate crops, overall land-use suitability, and market constraints must be considered before moving wheat into new areas. Site similarity analyses further suggest that the current distribution of wheat research sites in Ethiopia provides a reasonable coverage of the traditional wheat production area in terms of climatic conditions, and support the relevance of the Kulumsa station for wheat research throughout much of Eastern and Southern Africa.
ISSN: 1405-7484AGROVOC descriptors: Soft wheat; Wheats; Food production; Temperature resistance; Climatic factors; Precipitation; Climatic zones; Climatology; Ethiopia.AGRIS category codes: P40 Meteorology and Climatology; E14 Development Economics and PoliciesDewey decimal classification: 633.1
Printed in Mexico.
iii
Contents
Page
v Summary
1 Introduction
2 Materials and Methods
3 Overview of Wheat Production in Ethiopia
4 Results and Discussion
8 Conclusions
8 Acknowledgments
9 References
Tables
1 Table 1. Comparison of human population, per capita income, wheat area,
wheat production and other parameters for Ethiopia and other
countries in sub-Saharan Africa (from Aquino et al. 1996).
2 Table 2. Sites referred to in the text or indicated in Maps 1 or 7.
5 Table 3. Comparison of elevations and climate for four sites in Ethiopia
using data from the Ethiopian Country Almanac (ECA) and actual
meteorological station data (courtesy of EARO). Climate data are for
the wettest quarter.
Figures
3 Figure 1. Annual variation in climate at Kulumsa, Ethiopia.
4 Figure 2. Relationships between total precipitation (A) and elevation (B) and
mean minimum temperature during the wettest quarter for 180 wheat
germplasm accessions collected in Ethiopia.
7 Figure 3. Variation in wheat grain yield at Kulumsa, Ethiopia, as simulated
for changes in growing season total precipitation (A) and mean
temperature (B).
iv
Maps
Page
10 Map 1. Approximate distribution of traditional wheat production areas
of Ethiopia and the location of sites mentioned in this paper
(re-drawn from Belay et al. 1999)
10 Map 2. Approximate distribution of traditional wheat production areas
of Ethiopia superimposed on climatic zones of Ethiopia where
precipitation is over 350 mm and the mean minimum temperature
is between 6O and 11OC during the wettest quarter of the year.
The darkest areas in the southwest have a growing season greater
than 9 months, based on P/PE greater than 0.5.
11 Map 3. Areas of Ethiopia where precipitation is over 350 mm, the mean
minimum temperature is between 6O and 11OC during the wettest
quarter of the year, and the growing season is 9 months or less.
The vertically hatched zones represent elevations above 2000 m.
11 Map 4. Approximate distribution of traditional wheat production areas of
Ethiopia re-drawn from Belay et al. (1999), the proposed climate-
based wheat zone, and 180 wheat germplasm collection sites.
12 Map 5. Areas of Ethiopia where precipitation is over 350 mm, the mean
minimum temperature is between 6O and 11OC during the wettest
quarter of the year, and the growing season is 9 months or less.
The additional dark areas receive between 300 and 350 mm of
precipitation during the wettest quarter of the year.
12 Map 6. Areas of Ethiopia where precipitation is over 350 mm, the mean
minimum temperature is between 6° and 11°C during the wettest
quarter of the year, and the growing season is 9 months or
less. The additional dark areas have mean minimum temperatures
between 11º to 13°C during the wettest quarter of the year.
13 Map 7. Areas within Ethiopia having climatic conditions during the
wettest quarter that are similar to those of one of eight wheat
research sites in the country.
14 Map 8. Areas in sub-Saharan Africa having climatic conditions during the
optimal five-month growing season that are similar to those at
Kulumsa, Ethiopia.
v
Summary
This report describes a GIS-based assessment
of the distribution of wheat production in Ethiopia,
with emphasis on climatic factors limiting the
potential wheat area. Analyses relied primarily on
agro-climatological characteristics obtained from
interpolated climate data contained within the
Ethiopian Country Almanac; the same GIS-based tool
was used to analyze climatic data related to current
and potential wheat production areas in Ethiopia.
Based on consultations with Ethiopian wheat
scientists and examination of a published map
approximating the geographic distribution of current
wheat production, traditional rainfed wheat
production areas were best described in a zone with
350 mm or more precipitation and mean minimum
temperatures of 6OC to 11OC during the wettest
quarter (i.e., three consecutive months). The lower
altitude limit for this zone is roughly 2,000 m. The
wettest quarter was used to restrict planting to the
onset of the “meher” (long-season) rains; planting at
the onset of the “belg” (short-season) rains would
expose the maturing wheat crop to high rainfall
during the succeeding meher.
Precipitation and temperature limits were tested
further by comparing them to climatic conditions at
180 wheat germplasm collection sites in Ethiopia.
Results suggested a similar lower limit for precipitation
and minimum temperature range, but a higher upper
limit for minimum temperature range, although many
collections were made at lower sites (for example,
along major roads and in markets) that are warmer
than actual wheat growing areas.
Examining the potential for wheat cropping in
drier or warmer environments, it was found that
allowing production in areas with as little as 300 mm
of precipitation during the wettest quarter resulted in
the addition of a small area, primarily in the southeast
near the Sinana research station. In contrast, raising
the upper limit of the minimum temperature range by
2OC would perhaps double the potential wheat area
on the periphery of the highlands, due to a mean
rainfall of over 500 mm during the wettest quarter
in such areas. Thus, the present agro-climatological
constraint on wheat area is not lack of rainfall but
warm temperatures. This suggests that attempts
to identify new productive areas should focus
on strategies for overcoming heat stress and on
resistance to wheat diseases associated with warmer
environments, subject of course to soil suitability,
the presence of other crops, labor availability, and
other socioeconomic factors in the areas identified
for expansion.
On examining the distribution of eight wheat
research stations, we found that the present set of
stations covered most Ethiopian wheat zones and
exhibited little overlap. In a broader similarity analysis
for the Kulumsa station (a key center for wheat
research in Eastern Africa), the climate at that location
was similar to those of major wheat-producing areas
of Kenya and Ethiopia, as well as in the Great Lakes
Region (Rwanda, southwestern Uganda, and the
North Kivu district of the Democratic Republic of the
Congo), northern Tanzania, and Lesotho.
1
Introduction
Ethiopia is the second largest producer of wheat
in sub-Saharan Africa, following South Africa (Table
1). About 900,000 ha of bread (Triticum aestivum)
and durum (T. turgidum var. durum) wheats are
grown in Ethiopia, primarily as highland rainfed
crops. Mean wheat yields are around 1.4 t/ha, well
below experimental yields of over 5 t/ha (Hailu
1991). Ethiopia’s current annual wheat production
of approximately 1.3 million tons is insufficient to
meet domestic needs, forcing the country to import
30 to 50% of the annual wheat grain required.
The yield gap of over 3 t/ha suggests the potential
for increasing production through improved crop
management, particularly increased use of fertilizers.
However, there is also justification for examining
whether wheat production can be introduced to non-
traditional areas. Geographic information systems
(GIS) provide a way to do this, allowing researchers to
examine crop distribution in relation to climate and
other factors.
This paper first examines the current distribution
of wheat production in relation to climate. It then uses
the described climatic limits as the basis for evaluating
the potential for increasing wheat production area in
Ethiopia. To understand the possible contribution that
different research centers might make to improving
wheat production in current or potential wheat
areas, climate similarity analyses were conducted for
research stations used by the cooperative National
Wheat Research Program coordinated under the
auspices of the Ethiopian Agricultural Research
Organization (EARO).
Emphasis is given to the use of quantitative
characterizations based on climate data that have
been interpolated over all of Africa (Corbett and
O’Brien 1997). This ensures that mapped distributions
are more fully testable and reproducible, thus
contributing to a more precise understanding of
the adaptation of wheat in Ethiopia as well as in
other countries.
Table 1. Comparison of human population, per capita income, wheat area, wheat production, and other parameters for Ethiopia and other countries in sub-Saharan Africa (from Aquino et al. 1996).
Ethiopia Kenya South Africa Sudan Zambia Zimbabwe
Estimated population, 1995 (million) 58.6 28.3 41.5 28.1 9.5 11.3 Estimated growth rate of population, 1993-2000 (% per year) 3.0 2.5 2.2 2.7 2.6 2.2
Per capita income, 1994 (US $) 100 250 3,040 … 350 500 Average wheat area harvested, 1993-1995 (000 ha) 884 155 1,166 325 18 41
Average wheat yield, 1993-1995 (t/ha) 1.4 1.6 1.7 1.5 3.1 4.9 Average wheat production, 1993-1995 (000 t) 1,270 252 1,983 483 55 199 Average net imports of wheat, 1992-94 (000 t) 391 215 557 460 28 90
Nitrogen applied, 1993-1994 (kg N/ha) 5 23 60 87 62 160
An Agro-ClimatologicalCharacterization of Bread Wheat
Production Areas in Ethiopia
2
Materials and Methods
The primary data source for the climatic analyses
were the climate surfaces for Africa developed
by Corbett (1994) using thin plate smoothing
splines (Hutchinson 1995). In this technique, monthly
mean data for precipitation and temperature are
interpolated from point data corresponding to long-
term records of meteorological stations. This variant
of spline techniques allows use of data from a digital
elevation model (DEM, essentially a topographic map
converted to grid-based format) to improve the
estimation of variation in climate with elevation.
The DEM had a 2.5 arc-minute grid size, which
is roughly equivalent to a 5 km x 5 km grid size
for regions near the equator. In addition to the
basic climate variables, the set of surfaces includes
data for potential evapotranspiration (PET) and ratios
of precipitation to PET (P/PET). These variables are
provided both on an annual basis and for various
season models, including an optimal season defined
as the five-month period with the highest value of
P/PET and the wettest quarter defined as the three
consecutive months with the greatest precipitation.
Climate data for long-term monthly means at
specific sites were obtained from the FAO climate
database for Africa (FAO 1984). A list of the locations
considered in the current study is given in Table 2; the
locations are also shown in Map 1.
Zones for climate and site similarity within
Ethiopia were defined using the Ethiopia Country
Almanac (ECA), a component of the Country Almanac
Series of CD-ROM-based data sets and tools for
manipulating spatial data (Corbett et al. 1999).
Table 2. Sites referred to in the text or indicated in Maps 1 or 7.
Latitude Longitude Elevation Site (oN) (oE) (m) Comments
Addis Ababa 9.03 38.75 2,354 Capital city of Ethiopia, wheat production area, waterlogging on Vertisols .Adet† 11.27 37.48 2,240 Wheat research site, waterlogging on Vertisols, low soil fertility on Nitisols. Alemaya 9.50 41.02 1,950 Maize and wheat research site, moisture stress zone. Ambo 9.05 37.82 2,225 Key highland maize research site, waterlogging on Vertisols.Asasa 7.13 39.21 2,360 Wheat research site, relatively short growing season with terminal moisture stress. Awassa 7.05 38.47 1,750 Maize research site.Bekoji† 7.53 39.25 2,780 Wheat research site, high rainfall, long growing season. Debre Markos 10.35 37.73 2,440 Wheat production area, waterlogging on Vertisols .Debre Zeit† 8.73 38.97 1,900 Durum research coordinating center, waterlogging on Vertisols.Ginchi 9.03 38.15 2,250 Wheat research site, waterlogged Vertisol. Goba 7.02 39.98 2,710 Wheat production area, bimodal rainfall.Gondar 12.60 37.47 1,967 Wheat production area, high rainfall. Holetta† 9.05 38.50 2,400 Wheat research site, Septoria hotspot, waterlogging on Vertisols.Kulumsa† 8.00 39.15 2,200 National bread wheat research coordinating center. Mekelle† 13.30 39.29 2,050 Capital city of Tigray Region, frequent droughts. Sinana† 7.13 40.02 2,400 Wheat research site, bimodal rainfall. Weldiya†,‡ 11.75 39.60 2,320 Wheat production area.
† Sites characterized by climatic similarity analyses in Map 7.‡ Actual coordinates refer to a point approximately 20 km west of Weldiya town that corresponds to a wheat and
barley region (barley being grown at higher elevations).
3
Climate zones are defined through map overlay and
selection procedures. Zones of similar climate are
specified by characterizing the climate at the latitude
and longitude of the reference site and then selecting
criteria for similarity. For this study, the similarity
zones were usually based on the wettest quarter
(three-month period) and considered ranges of +/-
50 mm for precipitation and PET and of +/- 1oC for
mean maximum and minimum temperatures, unless
otherwise specified. For similarity analyses over all of
Africa, the Spatial Characterization Tool (Corbett and
O’Brien 1997) was used, assuming +/- 10% ranges
for the five most favorable months based on the ratio
P/PET. All maps are presented unprojected, by latitude
and longitude. To verify the limit of zones based on
climatic limits, conditions at specific locations were
also assessed. Presumed wheat production locations
were obtained based on collection sites of bread
wheats as listed in the USDA GRIN database (USDA-
ARS-NGRP 2000).
Simulations of wheat crop growth and
development were conducted using CERES Wheat
V3.50[98.0] (Hoogenboom et al. 1994; P. Wilkens,
personal communication, 1999). A 10-year set of
weather data from Kulumsa, Ethiopia, was used in
conjunction with a generic soil profile for a sandy
loam assumed to allow root growth to a depth
of 0.9 m. Seed was broadcast at a density of
180 plants/m2 and fertilized each year with 10 kg of
nitrogen. A window for sowing date from 1 July to 1
August was allowed.
Overview of WheatProduction in Ethiopia
In Ethiopia, wheat is grown primarily as a rainfed
crop by smallholders in the highlands (Map 1). In most
of the country, only a single wheat crop is grown
during the second, longer rainy season (meher)
which usually starts in June (Fig. 1). The short rains
(belg), starting in March, are less reliable in most
parts of Ethiopia; however, in the southeast of the
country (e.g., Bale zone of Oromiyia Region), rainfall
distribution is bimodal. Growing wheat in belg season
implies harvesting during meher, which often results
in high grain moisture levels and sprouting. Thus,
wheat crops are typically sown by broadcasting in
June or July and harvested in November or December
(Hailu 1991). A very small area has also been grown
as a winter crop under irrigation on state farms at
lower elevations (Jamal 1994). Pr
ecip
itat
ion
(m
m)
Month
Maximum temperature
Minimum temperature
PET
Precipitation
30
25
20
15
10
5
0
160
140
120
100
80
60
40
20
0J F M A M Jn Jl A S O N D
Figure 1. Annual variation in climate, Kulumsa, Ethiopia.
4
Bread wheat accounts for roughly 60% of total
wheat production and nearly all cultivars are derived
from modern, semi-dwarf wheats. Durum wheat
accounts for most of the remaining 40%, although
emmer wheat (T. dicoccum L.) is also grown. Bread
wheat is produced at slightly higher elevations
and on better drained soils than durum wheat,
which is primarily found on poorly drained Vertisols
(Hailu 1991).
Wheat production constraints include low soil
fertility, grass weed infestations, waterlogging in
Vertisol areas, and water deficits in short season areas
(Tanner et al. 1991). Stripe rust (Puccinia striiformis) is
common at higher elevations (> 2,400 m); stem rust
(P. graminis f. sp. tritici) is more problematic at mid-
elevations (2,000-2,400 m) (Bekele and Tanner 1995).
Double-cropping has recently been demonstrated
as a promising option for southeastern Ethiopia
(Tanner et al. 1994). In the Bale zone of Oromiya
Region, the belg rains are sufficiently long and reliable
for wheat or other crops. Double cropping could
reduce the negative effects of the current practice
of alternate season fallows: a continuous crop cover
would reduce erosion; alternating crops would help
control weeds; and human and animal power could
be used more efficiently.
Results and Discussion
Present wheat production areas
A review of growing season conditions for
various highland research sites suggested that
precipitation and minimum temperature were key
determinants of potential wheat areas. Setting
requirements of at least 350 mm rainfall and a
minimum temperature between 6° to 11°C during
the wettest quarter (three months) produced a
distribution map similar to the approximation of
traditional wheat production areas reproduced
from Belay et al. (1999; Map 2).
These limits, however, resulted in the inclusion
of a high rainfall area of southwestern Ethiopia that
is too wet for wheat production (annual precipitation
> 1,800 mm). Subsequent consultations indicated
that this area grows highland maize (Zea mays
L.) and enset (Musa abyssinica), which are better
suited to long, wet growing seasons. This zone was
thus excluded from the potential wheat area by
tightening the selection criteria to exclude areas
having a growing season greater than 9 months
(Map 2). The revised wheat zone closely corresponds
to sites exceeding 2,000 m in altitude (Map 3).
A. B.
Figure 2. Relationships between total precipitation (A) and elevation (B) and mean minimum temperature during the wettest quarter for 180 wheat germplasm accessions collected in Ethiopia.
Precipitation (mm)
0 200 400 600 800 1000
Elevation (m)
25
20
15
10
5
0
25
20
15
10
5
0
500 1500 2500 3500
5
To provide an independent estimate of appropriate
temperature and rainfall ranges for wheat production
zones, values for precipitation and mean minimum
temperature during the wettest quarter were obtained
for 180 bread wheat germplasm collection sites in
Ethiopia (Map 4). It is notable that most collection
points fell within the derived wheat production zone.
These data also support the lower limits of 350 mm
for precipitation and 6°C for minimum temperature
(Fig. 2A) used to develop our wheat distribution map.
However, the upper limit for minimum temperature
proved more problematic, with about half the collection
sites exhibiting minimum temperatures over 11°C
and nine sites having values over 15°C. Comparing
minimum temperature with elevation (as estimated
from the 5 km digital elevation model, not as reported
with the germplasm collection data) showed that
some collections came from locations well below the
suggested 2,000 m limit (Fig. 2B). Further inspection
of passport data for bread wheat accessions suggested
several possible explanations for these discrepancies.
Most accession data did not include information on the
type of collection, but in cases where this information
was recorded, the seeds often came from markets.
Thus, in many cases, samples may have come from
locations lower than where their source crops were
actually grown. It is also possible that some locations
were erroneously recorded. Hijmans et al. (1999) noted
that geographic coordinates reported for collection sites
exhibit high error rates.
The described results must also be qualified in
relation to possible sources of error in the climate
data and the difficulty in attributing objective
limits to ranges of adaptation or climatic similarity.
Although a formal error analysis is not possible,
indirect approaches can give some idea about the
reliability of characterizations.
The climate surfaces have errors attributable
to the source point data, the distribution of the
points, the 5 km grid size of the DEM, and the
interpolation procedure itself. One indicator of the
cumulative effects of these errors is to compare
interpolated values with actual observed data. Table
3 compares interpolated values from the ECA with
actual, measured values for Debre Zeit, Kulumsa,
Holetta, and Bekoji. Elevation figures were within
200 m of each other. Given the approximate relation
between elevation and temperature, whereby
temperature drops by roughly 0.6ºC per 100 m
increase in elevation (see Fig. 2B), this discrepancy
should result in an error of roughly 1ºC in
temperature. In effect, temperature discrepancies
were generally of this order and in the expected
direction. Minimum temperature at Holetta was
the notable exception, where a 95 m elevation
difference corresponded to a 0.4ºC temperature
difference opposite to the direction expected
based on the elevation effect. This suggests that
temperature errors in the current study were
generally less than 1ºC. The magnitude of the
Table 3. Comparison of elevations and climate for four sites in Ethiopia using data from the Ethiopian Country Almanac (ECA) and actual meteorological station data (courtesy of EARO). Climate data are for the wettest quarter.
Debre Zeit Kulumsa Holetta Bekoji
Data source: ECA Station ECA Station ECA Station ECA Station
Elevation (m) 2,046 1,900 2,130 2,200 2,495 2,400 2,996 2,780
Mean daily maximum temperature (°C) 23.3 24.2 21.9 21.1 20.0 19.8 16.2 17.2
Mean daily minimum temperature (°C) 11.7 12.4 11.0 10.9 9.1 8.7 5.9 7.7
Total precipitation (mm) 576 555 467 376 704 653 525 499
PET (mm) 300 -- 297 -- 257 -- 242 --
6
discrepancies were lower than those reported for a
similar study in highland Bolivia where a DEM with a
10 km grid cell size was used (Hodson et al. 1998).
Differences between interpolated and observed
precipitation values varied from 21 mm at Debre
Zeit to 91 mm at Kulumsa. Since there is often
no consistent relationship between elevation and
precipitation over large areas, these differences are
not readily attributable to differences between actual
elevation and DEM values. Unfortunately, current
methods for interpolating precipitation data are
extremely dependent on the number, distribution,
and quality of the point data. Models such as PRISM
attempt to improve the interpolations by accounting
for effects of prevailing winds, slope and aspect, and
weather systems (Natural Resources Conservation
Service Water and Climate Center 1998) and offer
hope for future improvements. Similarly, data on
cloud cover and temperature can be used to improve
estimates of rainfall in an area (Climate Prediction
Center 2000; Arkin and Ardanury 1989), although
values are typically reported on a 10 km grid.
Potential wheat production areas
Because water deficits and warm night
temperatures seemed to be key factors delimiting
bread wheat production areas in Ethiopia, potential
new areas for bread wheat production were identified
by assuming that technologies could be developed
to allow wheat to be grown in drier or warmer
environments. For drier conditions, such technologies
might include more drought tolerant cultivars,
supplemental irrigation from small catchments, or
agronomic practices—such as reduced tillage and
residue retention—that reduce runoff. Growing wheat
under warmer conditions might require cultivars
with greater heat tolerance as well as resistance
to pathogens that prevail under warmer conditions
(e.g., Helminthosporium sativum).
Applying the assumption that wheat will grow
in areas receiving as little as 300 mm during the
wettest quarter resulted in a surprisingly small
addition (4%) to the potential wheat production
area (Map 5). In contrast, a shift in adaptation
to include areas with 2°C warmer minimum
temperatures (e.g., up to 13°C) substantially
increase potential wheat area (Map 6). The actual
impact on total wheat area is impossible to
estimate: zones that meet climate criteria may
have unsuitable soils or topography or already
be used for other, more profitable agricultural
pursuits. However, as a rough indicator, increasing
the minimum temperature limit by 2°C expanded
the potential area suitable for wheat production by
108%.
These results seem counter-intuitive, given the
popular conception of Ethiopia as an arid, drought-
prone country. The principal explanation is that,
in terms of wheat cropping and ignoring year-to-
year variation, the Ethiopian highlands (to which
the wheat crop is so well-adapted) represent a
relatively humid environment. Precipitation during
the wettest three months is usually well in excess of
PET (Table 3; Fig. 1).
Representativeness ofcurrent wheat research sites
To examine whether the key wheat research
sites used by the National Wheat Research Program
of Ethiopia are representative of wheat production
areas in Ethiopia, site similarity analyses were
conducted for eight locations (Table 2). The sites
were found to cover a wide range of environments
(Map 7). Almost as important, the zones showed
little or no overlap, suggesting that the set of
research sites efficiently samples the current wheat
production area.
7
The area of wheat production identified as “20
km west of Weldiya” (Map 7) in Welo zone of the
Amhara Region is currently not served by a wheat
research station. Consultation with agronomists
familiar with the region confirmed that a limited
amount of wheat research is conducted on behalf
of the National Wheat Research Program by crop
scientists based at Sirinka, a sorghum research station
situated in a valley bottom at an altitude too low
for wheat (ca. 1,850 m). It was also reported that,
to address this deficiency, the Sirinka development
plan includes the establishment of substations in the
neighboring wheat production areas.
The ranges of precipitation, PET, and temperature
limits used in these similarity analyses (+/- 50 mm
and +/- 1°C) merit examination. The intention was to
use a range corresponding to yield differences that
are detectable in field trials. For potential grain yield
levels of 3,000 to 4,000 kg/ha, this might represent
a yield difference of 300 kg/ha. Using 10 years of
weather data at Kulumsa, simulations were run to
evaluate wheat yield response to precipitation and
temperature (Fig. 3). Reducing precipitation from the
mean of 540 mm to 490 mm over the growing
season decreased yields 430 kg/ha, whereas an
increase of 50 mm raised yields 345 kg/ha (Fig. 3A).
Reducing the maximum and minimum temperatures
during the growing season 1ºC (for a growing season
mean at Kulumsa of 16º C) increased wheat yields
about 140 kg/ha (Fig. 3B). This was attributable
mainly to a slight delay in maturity (120 days vs. 115
days for the actual weather). Increasing temperatures
1ºC decreased wheat yields 130 kg/ha, whereas an
increase of 2ºC reduced wheat yields 270 kg/ha.
These simulated results suggest that the limits used to
define site similarity zones are probably conservative.
A. B.
Figure 3. Variation in wheat grain yield at Kulumsa, Ethiopia, as simulated for changes in growing season total precipitation (A) and mean temperature (B).†
Precipitation (mm) Temperature (oC)
Gra
in y
ield
(kg
/ha)
Gra
in y
ield
(kg
/ha)
6000
5000
4000
3000
2000
1000
0200 300 400 500 600 700 800 900
6500
5000
4500
4000
3500
3000
2500
2000
1500
14.8 15.2 15.6 16 16.4 16.8 17.2 17.6 18
† Broken lines indicate +/- 2 standard deviations for simulations based on 10 years of weather data. The vertical lines indicate mean values over the growing season.
8
Because the Kulumsa research station is a
center of excellence for bread wheat research
in Eastern Africa and collaborates with other
national wheat research programs in the Eastern
and Central Africa Maize and Wheat Research
Network (ECAMAW), the similarity of its climate
to other sites in Eastern Africa was also
considered. A less restrictive set of criteria were
used for this exercise (i.e., +/- 20% of rainfall
and potential evapotranspiration and +/- 10%
of mean maximum and minimum temperatures),
given that the goals for transnational collaborative
research should be broader than those for a
sub-national research program. Furthermore, to
better compare Kulumsa conditions with those
of wheat production zones elsewhere in sub-
Saharan Africa, the five optimal months where
P/PE is greater than 0.5 were considered. The
results suggest that the climate at Kulumsa is
similar to conditions in major wheat-producing
areas of Kenya and Ethiopia, and significantly
congruent with those of wheat-producing areas
in the Great Lakes Region (Rwanda, southwestern
Uganda, and the North Kivu district of the
Democratic Republic of the Congo), northern
Tanzania, Lesotho, and South Africa (Map 8).
Of these areas, the only one not recognized
as significant for wheat production is the area
in South Africa and east of Lesotho. Wheat is
apparently not grown in this area due to several
factors, including the difficult terrain, competition
from traditional smallholder crops, and the
comparative advantage for the production of
wheat as a winter crop in the Mediterranean
climate of southwestern South Africa.
Conclusions
Our climate-based analyses suggest that the
greatest opportunity for expanding wheat production
area in Ethiopia would involve increasing the tolerance
of wheat to warmer growing conditions; this means
both heat tolerance and resistance to pathogens and
pests of warmer climates. However, any plans for
expanding wheat production must also consider other
factors, including the adaptation of current and/or
alternate crops, overall land-use suitability, and market
constraints. The similarity analyses further suggest
that the current distribution of wheat research sites
in Ethiopia provides a reasonable coverage of the
traditional wheat production area in terms of climate
conditions, and support the relevance of the Kulumsa
station for wheat research throughout much of
Eastern and Southern Africa. Overall, these results
demonstrate the utility of analyzing regional variation
in climate using tools such as those provided in the
Ethiopia Country Almanac.
Acknowledgments
Drs. Bedada Girma, Amanuel Gorfu, and Kidane
Georgis of EARO and Doug Clements of CIDA/
PSU-Ethiopia provided valuable information on the
relative importance of wheat in various regions
of Ethiopia. Adriana Rodriguez and Dave Hodson
helped significantly in processing the spatial data.
CIMMYT science writer Mike Listman and designer
Wenceslao Almazán collaborated to edit and produce
the publication. The authors express their gratitude
to the Environmental Systems Research Institute, Inc.,
for providing the ArcInfo and ArcView software. The
authors also appreciate the financial support provided
by the CIMMYT/CIDA Eastern Africa Cereals Program
to cover the cost of publishing this document.
9
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Map 1. Approximate distribution of traditional wheat production areas of Ethiopia and the location of sites mentioned in this paper (re-drawn from Belay et al., 1999).
Map 2. Approximate distribution of traditional wheat production areas (line figures) of Ethiopia superimposed on climatic zones of Ethiopia where precipitation is over 350 mm and the mean minimum temperature is between 6O and 11OC during the wettest quarter of the year (shaded areas). The darkest areas in the southwest have a growing season greater than 9 months, based on P/PE greater than 0.5.
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Map 3. Areas of Ethiopia where precipitation is over 350 mm, the mean minimum temperature is between 6O and 11OC during the wettest quarter of the year, and the growing season is 9 months or less. The vertically hatched zones represent elevations above 2000 m.
Map 4. Approximate distribution of traditional wheat production areas of Ethiopia re-drawn from Belay et al. (1999), the proposed climate-based wheat zone, and 180 wheat germplasm collection sites (the dots).
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Map 5. Areas of Ethiopia where precipitation is over 350 mm, the mean minimum temperature is between 6O and 11OC during the wettest quarter of the year, and the growing season is 9 months or less. The additional dark areas receive between 300 and 350 mm of precipitation during the wettest quarter of the year.
Map 6. Areas of Ethiopia where precipitation is over 350 mm, the mean minimum temperature is between 6° and 11°C during the wettest quarter of the year, and the growing season is 9 months or less. The additional dark areas have mean minimum temperatures between 11º to 13°C during the wettest quarter of the year.
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Map 7. Areas within Ethiopia having climatic conditions during the wettest quarter that are
similar to those of one of eight wheat research sites in the country.
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Map 8. Areas in sub-Saharan Africa having climatic conditions during the optimal five-month growing season that are similar to those at Kulumsa, Ethiopia.
Kulumsa